Laboratory: Chemical Kinetics 12 Chemical kinetics, also called reaction kinetics, is the study of reaction rates in chemical reactions. In simple terms, if two reactant molecules are to interact with each other, they must collide with sufficient energy to initiate the reaction. Two molecules that do not collide cannot react, regardless of how high their energies are. Conversely, two molecules that do collide, but with insufficient energy, cannot react. Intuitively, it's easy to understand that several factors affect reaction rates. Temperature affects reaction rates because molecules at a higher temperature have higher energies, and therefore any particular collision between reactant molecules is more likely to have the energy needed to initiate the reaction. Concentration affects reaction rates, because the number of reactant molecules is higher in more concentrated solutions, and therefore collisions between reactant molecules are more likely to occur. When one or more of the reactants is a gas, pressure affects reaction rates, because gases at higher pressures contain more molecules in a given volume (in effect, their concentration is higher). Finally, when one or more of the reactants is a solid, surface area affects reaction rates, because a larger surface area exposes more of the reactant molecules to collisions with the other reactant or reactants. In this chapter, we'll examine the effects of temperature, concentration, and surface area on reaction rates. Chapter 12 Laboratory: Chemical Kinetics 211